sigfox downlink issue

[francois]

Hi
When running the sigfox downlink exemple I do not receive any signal from the network.
Tx is correct I can see the message on the backend
downlink_callback function is correctly called (RX BEGIN and RX END message are printed)
I can see aswell that the DL arrow is green on sigfox backend.

But I never enter this code section in downlink_callback():
// Received one good frame
tfp_dump("RX=", rx_frame, length);

Meaning that no signal was received.
Thanks

[lcheminade]

In such a case it means that the downlink message was properly sent by the basestation but never received by the module. Try to improve the RF link by going closer to a window our outside.

[francois]

Does it mean that the link budget on DL is supposed to be worse than the one on UL?

[lcheminade]

Yes. Plus the fact the downlink message is emitted once compare to the uplink message which is emitted three times.

[francois]

I did some tests outdoor. The UL SNR checked on sigfox backend is quiet good : SNR=21dB.
Even at this level I can't see any donwlink signal. Does it sound possible to you?

[lcheminade]

Could you please give me your Sigfox ID so that I can check?

[francois]

I perform the tests with several devices.
One of the device is 1BC09.

[eliotstock]

What was the resolution of this issue please? I have the same issue with a bunch of our modems, running fields tests in central London. One of them is 1AEB2. Here's a log from my firmware when waiting for the downlink message. The actual payload of the downlink message is lost:

:INFO:Alert attempt #1
EBUG:Modem: UART to modem: AT$SB=1,2,1
EBUG:Modem: Waiting up to 10s for command response
EBUG:Modem: UART from modem: AT$SB=1,2,1
OK

EBUG:Modem: Stopping response timer
EBUG:Modem: OK
EBUG:Modem: Waiting up to 55s for RX response
EBUG:Modem: UART from modem: +RX BEGIN
+RX END
EBUG:Modem: Stopping response timer

When I see only:

+RX BEGIN
+RX END

with no payload in between, what does that indicate? Can I be sure that at least the uplink message has been received by the base station? Because I'm pretty sure I've seen this behaviour when the uplink has NOT hit the base station according to backend.sigfox.com. At the moment, I'm not that bothered about the contents of the downlink message, but I do need a reliable ACK on the device for the uplink message.